b 1. Field of the Invention
This invention relates generally to a material handling car and track assembly and is directed more particularly to a synchronous drive and braking means mounted in the track assembly and adapted to influence the speed of the car.
2. Description of the Prior Art
It is generally known in car and track systems to propel and control the speed of a plurality of cars on tracks by means of wheels, the wheels being adapted to engage the cars in order to accelerate or decelerate the cars.
U.S. Pat. No. 4,656,949, issued Apr. 14, 1987 to Ragot, discloses a device for gripping and transferring a receptacle using synchronous endless chains with drive fingers mounted on adjustable modules, the drive fingers engaging a handle on the receptacle and pulling the receptacle along.
U.S. Pat. No. 4,564,100, issued Jan. 14, 1986 to Moon, discloses a device for conveying a plurality of carriers over a path for work to be performed on the articles supported by the carriers in successive work stations, comprising vertical drive wheels which engage the underside of the carrier and accelerate or decelerate the car. The car rides on the drive wheels. Guide rollers are provided for engagement with the sides of the carriers to guide the carriers laterally. Swivel wheels are provided to prevent the carrier's casters from contacting the drive wheels. The carriers are towed by dogs on a main conveyor movable along the floor. Moon discloses sensing means which provide for advancing the carrier to a next work station.
U.S. Pat. No. 4,503,778, issued Mar. 12, 1985 to Wilson, discloses a device for the transportation of people, comprising three track rails upon which trolleys ride, the trolleys including three wheels which interlock with the rails, a driving and braking means comprising a pair of horizontal driving and braking wheels which are adapted to engage opposite sides of a single vertically extending keel depending from the bottom of a carrier.
U.S. Pat. No. 4,530,287, issued Jul. 23, 1985 to Sticht, discloses a device for transporting workpieces in an assembly line, comprising guide means including two guide tracks, with one guide track having two hardened guide rollers mounted on the underside of a pallet and adapted to engage the the lateral guide track. Sticht also discloses advancing means comprised of elastic conveyor rollers above the track which advance the pallets along the tracks by means of a drive chain. The lateral guidance of the pallet is effected solely by one lateral guide track in engagement with its corresponding guide rollers, in cooperation with the conveyor rollers.
U.S. Pat. No. 3,361,083, issued Jan. 2, 1968 to Babson, discloses a device for carrying articles between work stations, comprising drive means which comprises center drive wheels, a sprocket disposed within the center drive wheel adapted to engage a drive chain which extends the length of a housing, and rack drive wheels mounted on axles above and below the center drive wheels, the lower end of one axle mounted on a link bar and the upper end connected to a pivot arm extending from a shaft of the center drive wheel, with a link bar enabling the rack drive wheels to be pivoted about the axes of the central drive wheels.